Hydrosilylation chemistry, typically involving a reaction between a silyl hydride and an unsaturated organic group, is the basis for synthesis routes to produce commercial silicone-based products like silicone surfactants, silicone fluids and silanes as well as many addition cured products like sealants, adhesives, and silicone-based coating products. Heretofore, hydrosilylation reactions have been typically catalyzed by precious metal catalysts, such as platinum or rhodium metal complexes.
Various precious metal complex catalysts are known in the art. For example, U.S. Pat. No. 3,775,452 discloses a platinum complex containing unsaturated siloxanes as ligands. This type of catalyst is known as Karstedt's-catalyst. Other exemplary platinum-based hydrosilylation catalysts that have been described in the literature include Ashby's catalyst as disclosed in U.S. Pat. No. 3,159,601, Lamoreaux's catalyst as disclosed in U.S. Pat. No. 3,220,972, and Speier's catalyst as disclosed in Speier, et al., J. Am. Chem. Soc., 1957, 79, 974.
Recently, new and inexpensive non-precious metal-based complexes containing a tridentate nitrogen ligand have been found to selectively catalyze hydrosilylation reactions, as described in the U.S. Patent Application Publication Nos. 2011/0009573 and 2011/0009565, the contents of both publications incorporated herein by reference in their entireties. In addition to their low cost and high selectivity, the advantage of these catalysts is that they can catalyze hydrosilylation reactions at room temperature while precious metal-based catalysts typically work only at elevated temperatures.
A five-coordinate Fe(II) complex containing a pyridine di-imine (PDI) ligand with isopropyl substitution at the ortho positions of the aniline rings has been used to hydrosilylate an unsaturated hydrocarbon (1-hexene) with primary and secondary silanes such as PhSiH3 or Ph2SiH2 (Bart, et al., J. Am. Chem. Soc., 2004, 126, 13794) (Archer, et al. Organometallics, 2006, 25, 4269). However, it was believed that these catalysts are only effective with the aforementioned primary and secondary phenyl-substituted silanes, and not with, for example, alkoxy substituted silanes such as (EtO)3SiH.